A member of the second Jesuit expedition to the planet Rakhat, Sean is the mission's chemist, charged with studying and bringing back Rakhati nanotechnology. His father David is Jewish and his mother Maura is a member of the revolutionary Sinn Fein party in Ireland. Sean is enormous, like all members of the second mission, and morose to the point that the father superior considers him a pain in the ass, but acknowledges that poetry dwells in his soul. Sean believes that parish clergy are now allowed to marry as a lesser evil to ordaining women. He believes that celibacy requires a firm sense that God uses it to serve others without exclusion—and also misses the days when "pointless self-denial" had been a major part of Catholicism (Chap. 15, p. 154).